There are 5 different detectives to play. Each detective plays significantly different from every other detective.
Each detective has 3 plots (except Ray, with 2). No detective sees all of his or her plots in a given game. Every plot has 4 different endings.
There are 6 different murders to investigate. Each murder has fairly game-changing rules, as in Arkham Horror.
Each murder has 3 different murder-specific events, only 1 of which gets used each game. These are usually fairly significant events. This is ignoring the
deck of 20 or so generic events that can go off each game.
If you're reasonably generous, that's 1,000s of different game setups to play. Even if you apply a more cynical view, that's still 30 unique game experiences, or between 60-120 hours of play before you start repeating anything.
Besides that, I feel that Android is fun in and of itself. Like Descent, a given murder will play out in many different ways, so even if you play the exact same setup over and over, you'll still get a different play experience each time.